Summary of Significant Accounting Policies - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($) segment	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of reportable segments | segment	1
Change in discount rate, bookings	2.00%
Change in fair value of Bookings commitments	$ 3,890
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Accrued and other current liabilities	Accrued and other current liabilities
Total stockholders' deficit	$ 161,992	$ 111,400	$ 57,136
Accumulated Deficit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total stockholders' deficit	1,052,897	1,003,210	946,884
Additional Paid-In Capital
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total stockholders' deficit	$ (891,105)	(891,583)	$ (889,955)
Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total stockholders' deficit		5,746
Cumulative Effect, Period of Adoption, Adjustment | Accumulated Deficit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total stockholders' deficit		(8,572)
Cumulative Effect, Period of Adoption, Adjustment | Additional Paid-In Capital
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total stockholders' deficit		14,318
Cumulative Effect, Period of Adoption, Adjustment | Accounting Standard Updated 2020-06 | Additional Paid-In Capital
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total stockholders' deficit		14,318
Cumulative Effect, Period of Adoption, Adjustment | Accounting Standards Update 2020-06 | Accumulated Deficit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total stockholders' deficit		$ 8,572
Software and Software Development Costs
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Estimated useful life	3 years